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9) given

velcoity is dependent on elasticity and density

Now dimensionally

$$\begin{gathered} v=\left[M^0{L}^1{T}^{-1}\right] E=\left[M^1{L}^{-1}{T}^{-2}\right] and Density = \left[M^1{L}^{-3}\right] \\ so matching coeffcients \\ L.H.S we have M=0, L=1 and T=-1 \\ R.H.S = \frac{E}{\rho } gives L= 3-1=2 \\ thus to match L.H.S we have to take \\ v=\sqrt{\frac{E}{\rho }} \\ for checking: \\ R.H.S \\ M=0 \\ L=1 \\ T=-1 \end{gathered}$$ 
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